1. Field of the Invention
The present invention relates to an optical fiber switching apparatus that can be used in a coupling portion which performs operations such as switching for systems in which optical fibers are coupled so as to constitute a fiber optic network or the like.
2. Description of the Prior Art
Although an optical fibers have been used in trunk line communication systems, research aimed at introducing fiber optic network systems is currently being conducted. Unlike systems which repeat transfers from point to point, it is necessary for a fiber optic network system to provide superior serviceability and efficiency for the distributed users which are on the same level. In order to design such a fiber optic network system, it is important to provide a switching apparatus such as, for example, an optical cross-connection apparatus, an optical switch board, etc. for switching the optical fibers without adversely affecting the light signals transmitted therein.
Apparatuses such as the optical cross-connection apparatus are often referred to as "huge optical switches". Although various research is being conducted, it has proven difficult to develop a relatively small optical switch which has multiple inputs and multiple outputs. The difficulty arises because the number of coupled lines becomes large when optical fibers are coupled in a network. The optical fibers become so crowded that the working efficiency of the coupled optical fiber decreases drastically. It is also possible for the optical fibers to be misconnected. Moreover, the overcrowding of the optical fibers becomes even more severe when a coupling point is intended to be switched to another terminal.
A conventional optical switch which has been used for the aforementioned switching is a "1.times.N" (i.e. single.times.plural) type optical switch. In a 1.times.N type optical switch, a single-core connector is disposed on the "1-side" (i.e. single-side) while a plurality of single-core connectors are disposed on the "N-side" (i.e. plural-side) on the same level. Thus, the single-core connector on the 1-side is carried by a switching mechanism, thereby allowing the 1-side single-core connector to be coupled with a desired connector on the N-side.
Another conventional optical switch is a "N.times.M" (i.e. plural.times.plural) type optical switch. In an N.times.M type optical switch, a plurality of guide rails disposed in the direction perpendicular to each other are provided. The optical fibers are attached to slide terminals which can move along a corresponding one of the guide rails. Thus, the slide terminals are moved by a switching mechanism so as to make a connection between desired optical fibers. Such an optical fiber connection switching apparatus is disclosed in Unexamined Japanese Patent Publication No. Hei-3-287212.
Optical fibers are connected with each other by placing an end surface of one optical fiber so that it is opposite to an end surface of another optical fiber. A driving mechanism is then used to move, position and hold the optical fiber. A conventional optical fiber driving mechanism is one that holds an optical fiber by use of a pair of driving rollers, and rotates the driving rollers so as to move the optical fiber which is being held. This type of driving mechanism has been used as a means for placing optical fibers so that they are opposite to each other.
Each of the aforementioned optical switches can adequately be applied in a limited number of special conditions. However, various problems occur when a large number of optical fibers are used in optical fiber network. For example, if switching is required when there are a large number of optical fibers, it is necessary to miniaturize and integrate the optical while maintaining the ease of operation thereof. However, as mentioned above, it is difficult to make relatively small optical switches.
If a switch having the function of an N.times.M type optical switch is intended to be realized through the use of conventional 1.times.N type optical switches, at least (M) 1.times.N type optical switches would be required. For example, if a switch having a function of 8.times.12 were required, (12) 1.times.8 type optical switches would have to be used. Thus, It is difficult to miniaturize the apparatus due to the space which is occupied by each of the 1.times.N type optical switches. On the other hand, in a true N.times.M type optical switch, it is possible to miniaturize the apparatus in comparison with a switch having the same function but being comprised of 1.times.N type optical switches. However, a switching mechanism would be required in the true N.times.M type optical switch for moving respective slide terminals on the N-side and the M-sides along their corresponding guide rails.
If it is necessary to switch a plurality of slide terminals at the same time, a plurality of such switching mechanisms would be needed. The number of switching mechanisms required would be equal to the total number of optical fibers (i.e. N+M). Thus, miniaturize the N.times.M type optical switch is difficult. Moreover, highly rigid guide rails are needed for positioning the slide terminals with a high degree of accuracy. Therefore, it is impossible to miniaturize the slide terminals or the guide rails. Accordingly, a large switching mechanism causes design problems.
On the other hand, in a conventional optical fiber driving mechanism, the pair of driving rollers which are holding an optical fiber are merely rotated so as to move the optical fiber. Therefore, the structure of the driving mechanism can readily be achieved. However, there are many problems with the miniaturization of this type of optical switch which are similar to the problems encountered with the miniaturization of the aforementioned switching mechanism used in N.times.M type optical switches. For example, when driving mechanisms are used in an N.times.M type optical switches, a driving mechanism must be provided for each optical fiber on the N-side and the M-side, thereby making it difficult to miniaturize the optical switch. Moreover, when a driving mechanism is used, it becomes necessary to position a slide terminal with a high degree of accuracy. Therefore, it is necessary to provide a device, which is separate from the driving mechanism, so as to ensure a high degree of accuracy in the positioning of the slide terminal. This added device cause the cost of the optical switch to increase.